[(1-tetralinyl)alkyl]piperazines - American Chemical Society

Roberto Perrone,* Francesco Berardi, Marcello Leopoldo, and Vincenzo Tortorella ... Pharmacia S.p.A., via Giovanni XXIII, 23, 20014 Nerviano (MI), Ita...
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J. Med. Chem. 1996, 39, 3195-3202

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1-Aryl-4-[(1-tetralinyl)alkyl]piperazines: Alkylamido and Alkylamino Derivatives. Synthesis, 5-HT1A Receptor Affinity, and Selectivity. 31 Roberto Perrone,* Francesco Berardi, Marcello Leopoldo, and Vincenzo Tortorella Dipartimento Farmaco-chimico, Universita` di Bari, via Orabona, 4, 70126 Bari, Italy

Maria Gioia Fornaretto, Carla Caccia, and Robert A. McArthur Pharmacia S.p.A., via Giovanni XXIII, 23, 20014 Nerviano (MI), Italy Received January 29, 1996X

The synthesis and binding profile on 5-HT1A, 5-HT2, D-1, D-2, R1, and R2 receptors of the N-4 long-chain arylpiperazines 22-40 are reported, where an amino or amido function is inserted into the intermediate chain linked to the R position of the tetralin nucleus. Unlike the buspirone analogues, for the amido derivatives studied in this paper, the terminal amide function of longchain piperazines is not important for 5-HT1A receptor affinity binding, and its removal yields high-affinity 5-HT1A receptor agents. Serotonin (5-hydroxytryptamine, 5-HT) is involved in many physiological and pathophysiological processes in the brain which are mediated by the specific interaction of 5-HT with several different receptors. The classification of these receptor subtypes, their role, and their respective ligands are reported in several recent reviews.2-8 The 5-HT1A receptors are to date the bestcharacterized subtypes, and it is generally accepted that they are involved in psychiatric disorders such as depression and anxiety. Several compounds from different chemical classes possess high affinity for 5-HT1A receptors.8 Among these, some long-chain arylpiperazine compounds with a terminal amide fragment, such as buspirone (1) and ipsapirone (2) are effective antianxiety and antidepressant drugs.

However, even if the long-chain arylpiperazines represent the class most throughly studied to date, their selectivity versus dopaminergic D-2 and adrenergic R receptors is not yet clear, with the result that several papers have been published by different researchers.9-12 In order to contribute toward solving this problem, in two recent papers1,13 we have described a new model of long-chain arylpiperazines, with a dihydronaphthalene or tetralin nucleus on the terminal part of the side chain. Since for these compounds the affinity and selectivity values on the 5-HT1A receptor were very encouraging, and since we noted that the incorporation of an amine function into the spacer, in place of a methylene group, as in compound 3, causes an increase in selectivity versus D-2, R1, and R2 receptors compared to the corresponding compounds 4, we decided to insert * To whom correspondence should be addressed. X Abstract published in Advance ACS Abstracts, July 1, 1996.

S0022-2623(96)00087-8 CCC: $12.00

an amine or amide function into the methylene spacer between the basic nitrogen atom and the tetralin nucleus.

On the other hand, Misztal et al.14 assumed that the terminal amide fragment in buspirone-like ligands stabilized the 5-HT1A receptor-ligand complex by either π-electron or local dipole-dipole interaction. However, although a hydrocarbon chain with a terminal amide fragment significantly influences the ability to bind to other receptors, its role is not yet clear. In the present paper, we therefore report the synthesis and the binding profile on 5-HT1A, 5-HT2, D-1, D-2, R1, and R2 receptors of the N-4 long-chain arylpiperazines 22-40 (Table 1) where the -CONHR or -CH2NR or -NRCH2 or -NHCO function is linked to the R position of the tetralin nucleus, in place of two methylene groups which were present in the previously reported arylpiperazines.1 The arylpiperazine and tetralin moieties used for the compounds in the present work are those present in agents with the highest affinity for the 5-HT1A receptor;13 they are 1-(2-methoxyphenyl)-, 1-phenyl-, and 1-(2-pyridyl)piperazine and 5-methoxy-1,2,3,4-tetrahydronaphthalene. Some compounds present a methyl group on the nitrogen atom of the amide function (28-30), or of the amine function (36), to prevent a possible intramolecular hydrogen bond. Chemistry Synthesis of the final compounds is illustrated in Scheme 1. Compounds derived from 5-methoxy-1,2,3,4tetrahydronaphthalene-1-carboxylic acid (9) were prepared by reacting 5-methoxy-1-tetralone (8) with trimethylsilyl cyanide, giving the trimethylsilyl cyanohydrin derivative, according to the literature.15 This was hydrolyzed, dehydrated, and then reduced in a single © 1996 American Chemical Society

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Table 1. Physical Properties

compd

X

Y

Ar

formulaa

mp, °C

recryst solv

3b

NH CH2 CH2 CH2 CH2 CO CO CO CO CO CO CO CO CO CH2 NH NH NH NH N(CH3) NH NH NH NH

CH2 CH2 CH2 CH2 CH2CH2 NHCH2 NHCH2 NHCH2 NHCH2CH2 NHCH2CH2 NHCH2CH2 N(CH3)CH2 N(CH3)CH2 N(CH3)CH2CH2 NHCH2 CH2 CH2 CH2CH2 CH2CH2 CH2 CO COCH2 COCH2 COCH2

2-CH3O-Ph 2-CH3O-Ph Ph 2-Py 2-CH3O-Ph Ph 2-CH3O-Ph 2-Py Ph 2-CH3O-Ph 2-Py Ph 2-CH3O-Ph Ph Ph Ph 2-Py Ph 2-CH3O-Ph 2-CH3O-Ph Ph Ph 2-CH3O-Ph 2-Py

C24H31N3O2‚HCl C25H33N3O3‚2HCl C23H30N4O2‚3HCl C25H33N3O2‚2HCl C26H35N3O3‚2HCl C24H32N4O2‚2HCl‚3/2H2O C25H33N3O2‚HCl‚H2O C26H35N3O3‚2HCl C26H35N3O2‚2HCl C24H33N3O‚3HCl C23H31N3O‚2HCl‚2/3H2O C22H30N4O‚3HCl‚1/2H2O C24H33N3O‚2HCl C25H35N3O2‚2HCl‚2/3H2O C25H35N3O2‚2HCl‚5/3H2O C23H29N3O2‚HCl C24H31N3O2‚2HCl C25H33N3O3‚2HCl C23H30N4O2‚2HCl‚1/2H2O

235-239 dec 150 dec 210 dec 180-185 dec 194-196 213 dec 257-259 175-178 dec 199 dec 242 dec 247 dec 156-159 dec 261-263 dec 144-147 dec 141-144 dec 244 dec 200-203 dec 211-213 251-253 dec

MeOH CH2Cl2/Et2O MeOH/Et2O MeOH/Et2O CH2Cl2/Et2O MeOH/Et2O MeOH/Et2O CH2Cl2/petroleum ether MeOH/Et2O MeOH/Et2O CH2Cl2/Et2O CH2Cl2/Et2O MeOH/Et2O CH2Cl2/Et2O MeOH/Et2O MeOH/Et2O MeOH/Et2O MeOH/Et2O MeOH/Et2O

4b 5b 6b 7b 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 a

Analyses for C,H,N; results were within (0.4% of the theoretical values for the formulas given. b Formerly published compounds.1,13

Scheme 1a

a Reagents: (A) (CH ) SiCN, ZnI ; (B) concentrated HCl, CH COOH, SnCl ‚H O; (C) DCC; (D) LiAlH ; (E) p-toluenesulfonic acid; (F) 3 3 2 3 2 2 4 NaBH4; (G) CH3OCOCl; (H) NH2OH‚HCl, CH3COONa; (I) H2, Pd/C (10%); (J) BrCH2COCl or ClCH2CH2COCl; (K) N-arylpiperazines. b P, 4-phenylpiperazin-1-yl; M, 4-(2-methoxyphenyl)piperazin-1-yl; PY, 4-(2-pyridyl)piperazin-1-yl.

step to obtain compound 9. Then amides 22-30 were obtained by reacting compound 9 with the corresponding amines 11-19, synthesized as already described,16,17 in the presence of 1,3-dicyclohexylcarbodiimide (DCC). Amine 31 was prepared from amide 22 by reduction with LiAlH4. Amines 11-19 were also used to obtain amines 3 and 32-35 according to a recently reported synthetic pathway.1 The N-methylated derivative 36

was obtained by treating 3 with methyl chloroformate18 to yield its carbamate, which was then reduced with LiAlH4. In order to prepare the naphthalenamine amidic derivatives, 5-methoxy-1,2,3,4-tetrahydro-1naphthalenamine (10) was synthesized by catalytic hydrogenation of the oxime of 5-methoxy-1-tetralone (8), as reported.19 Then amine 10 was acylated with bromoacetyl chloride or 3-chloropropionyl chloride to give

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Table 2. Binding Affinitiesa and Selectivities IC50, nM compd 3 4 5 6 7 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 buspirone 8-OH-DPAT ketanserin haloperidol prazosin yohimbine

5-HT1A [3H]-8-OH-DPAT

5-HT2 [3H]ketanserin

D-2 [3H]spiroperidol

R1 [3H]prazosin

R2 [3H]yohimbine

7.7 ( 0.8 0.77 ( 0.09 0.50 ( 0.05 0.54 ( 0.06 1.73 ( 0.22b 416 ( 37 35 ( 3 173 ( 20 63 ( 7 16 ( 2 95 ( 9 271 ( 20 307 ( 30 134 ( 13 116 ( 13 92 ( 6 49 ( 5 53 ( 5 10 ( 2 8.7 ( 1.9 5310 ( 580 311 ( 32 38 ( 6 135 ( 19 30 ( 3 2.1 ( 0.2

2580 ( 150 330 ( 30 230 ( 30 250 ( 20 NTc 1560 ( 160 1710 ( 160 1270 ( 130 349 ( 40 2040 ( 160 428 ( 31 848 ( 75 1070 ( 100 134 ( 12 1900 ( 130 2720 ( 350 9140 ( 820 2690 ( 80 3300 ( 300 1740 ( 250 >10 000 1200 ( 70 841 ( 83 726 ( 83 >10 000 >10 000 3.4 ( 0.3

380 ( 40 18 ( 2 110 ( 20 140 ( 10 15.4 ( 0.8b 4040 ( 440 448 ( 51 2440 ( 230 783 ( 82 116 ( 13 819 ( 26 882 ( 71 332 ( 45 594 ( 55 1100 ( 170 1200 ( 150 1850 ( 200 2160 ( 190 1060 ( 90 73 ( 8 >10 000 2970 ( 390 761 ( 62 1900 ( 200 280 ( 30 5.2 ( 0.6

220 ( 20 6.5 ( 0.6 43 ( 5 66 ( 7 78.3 ( 5.5b 427 ( 46 166 ( 16 838 ( 61 19 ( 2 84 ( 9 327 ( 48 510 ( 22 297 ( 29 159 ( 10 1150 ( 120 790 ( 76 725 ( 55 626 ( 65 881 ( 103 887 ( 62 5980 ( 390 313 ( 8 153 ( 7 534 ( 57 >10 000 >10 000

280 ( 40 17 ( 2 260 ( 30 48 ( 5 NTc 1850 ( 290 1380 ( 140 7220 ( 70 186 ( 20 564 ( 48 746 ( 80 250 ( 37 183 ( 21 144 ( 16 1420 ( 180 310 ( 47 95 ( 11 788 ( 98 458 ( 57 112 ( 10 >10 000 2680 ( 450 1250 ( 140 1330 ( 270 >10 000 810 ( 80

selectivity vs 5-HT1A receptor, IC50 ratio 5-HT2 D-2 R1 R2 335 429 460 463 4 49 7 6 128 5 3 4 1 16 30 187 51 330 200

49 23 220 259 9b 10 13 14 12 7 9 3 1 4 10 13 38 41 106 8

4 22 5

10 20 14

29 8 86 122 45b 1 5 5 0.3 5 3 5 1 1 10 8 15 12 88 102 1 1 4 4

36 22 520 89 4 40 42 3 35 8 1 1 1 12 3 2 15 46 13 9 33 10

4.8 ( 0.5 1.4 ( 0.6 30 ( 3

a

Compounds 22-40 showed very high affinity binding values on D-1 receptor (IC50 > 1000 nM). b Previously published data,1 here reported for comparison. cNot tested.

the intermediates 20 and 21, respectively. The amination of these halo derivatives with the appropriate N-arylpiperazine provided the final amides 37-40. Pharmacology Final compounds (Table 2) were evaluated for in vitro affinity on dopamine D-1 and D-2, serotonin 5-HT1A and 5-HT2, and adrenergic R1 and R2 receptors by radioligand binding assays. All the compounds were used in the form of hydrochloride salts and were water-soluble. The following specific radioligands and tissue sources were used (a) dopamine D-1 receptorss[3H]SCH-23390, rat striatal membranes; (b) dopamine D-2 receptorss [3H]spiroperidol, rat striatal membranes; (c) serotonin 5-HT1A receptorss[3H]-8-OH-DPAT, rat hippocampus membranes; (d) serotonin 5-HT2 receptorss[3H]ketanserin, rat brain prefrontal cortex membranes; (e) R1-adrenergic receptorss[3H]prazosin, rat brain cortex membranes; (e) R2-adrenergic receptorss[3H]yohimbine, rat brain cortex membranes. Concentrations required to inhibit 50% of radioligand specific binding (IC50) were determined by using eight to nine different concentrations of the drug studied. Specific binding was defined as described in the Experimental Section under Pharmacological Methods; in all binding assays, it represents more than 80% of total binding, except for R2 (>60%). The results were analyzed by using the LIGAND program to determine IC50 values. Results and Discussion The results of the binding assays are illustrated in Table 2. Considering as a term of comparison the three

methylene-spaced arylpiperazine derivatives 4-6 (see Table 1), which had been previously studied1 and were reinvestigated in the Pharmacia laboratories (IC50 ) 0.77, 0.50, and 0.54 nM, respectively, for the 5-HT1A receptor), it should be noted (see Figure 1) that replacing the R-methylene group in the spacer with a secondary amine group, as for the corresponding compounds 3, 32, and 33, respectively, led to a decrease in affinity for the 5-HT1A receptor, less so for the first compound (IC50 ) 7.7 nM) than for the other two (IC50 ) 92 and 49 nM, respectively). Compound 36, an N-methyl derivative of 3, showed a similar affinity value to 3 (IC50 ) 8.7 nM). On the other hand, it should be noted that the insertion of an amine function into the 1-(2-methoxyphenyl)piperazine derivative 3 led to an increase in selectivity versus D-2 and R receptors, compared to the corresponding reference compound 4, whereas for the phenyl and 2-pyridyl derivatives 32 and 33 we observed a decrease in selectivity compared to 5 and 6, respectively. Finally, the three-membered amidic derivative 37 proved to have negligible affinity for 5-HT1A receptor (IC50 ) 5310 nM) compared to the corresponding amino derivative 32 and the reference compound 5. We can therefore deduce that, for those derivatives with three atoms in the spacer, a basic moiety at the end of the alkyl chain is required for better affinity than an amide function. Among the amino derivatives, the 1-(2-methoxyphenyl)piperazine derivative 3 proved to have the highest affinity and selectivity for 5-HT1A receptor. The values of affinity and selectivity for the arylpiperazine derivatives with four atoms in the spacer showed the same behavior. In this case the previously

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Figure 1.

studied1 arylpiperazine derivative 7 (see Table 1), with an alkyl spacer of four methylene units (IC50 ) 1.73 nM), was used as a term of comparison. It should be noted that the corresponding amino compound 1-(2-methoxyphenyl)piperazine derivative 35 showed a slight decrease in affinity (IC50 ) 10 nM) whereas the amino compound of the 1-phenylpiperazine derivative 34 showed a more remarkable decrease (IC50 ) 53 nM). Regarding the selectivity versus D-2 and R1 receptors, we observed the same behavior as above; in fact, the amino derivative of 1-(2-methoxyphenyl)piperazine showed a higher selectivity than the corresponding reference compound 7, whereas for derivative 34 the selectivity was lower. For the amido derivatives with four atoms in the spacer, both those derived from 1-aminotetralin, 3840, and those derived from 1-tetrahydronaphthoic acid, 22-24, showed lower affinity for 5-HT1A receptor than the corresponding amino compounds 34 and 35. However, among these amido compounds, the 1-(2-meth-

oxyphenyl)piperazine derivatives showed moderate affinities (IC50 ) 35-38 nM), whereas the others proved to have low affinity, and the relative selectivity values were very poor. The insertion of the methyl group on the amide function, as in 28 and 29, led to no advantage for affinity. The displacement of the amino group in the intermediate chain from the R position, as in 34, to the β position, as in 31, led to a decrease in affinity. The lengthening of the intermediate chain from four to five atoms in amido derivatives 25-27 and 30 led to a significant improvement in the affinity for 5-HT1A receptor, and in this group also, the 1-(2-methoxyphenyl)piperazine derivative 26 showed the highest affinity (IC50 ) 16 nM). As for the affinity for D-1 and 5-HT2 receptors, the IC50 values were very high, making it impossible to carry out a structure-activity relationship (SAR). In conclusion, in comparison with the arylpiperazine derivatives 4-7,1 bearing a methylene spacer, of which

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the 1-(2-methoxyphenyl)piperazine compound 4 was the least selective, the insertion of an amine function into the corresponding compound led to a slight decrease in affinity and an increase in selectivity only in the 2-methoxyphenyl derivatives 3 and 35. By contrast, a worsening of affinity and selectivity derives from the insertion of an amide function, even though the lengthening of the intermediate chain led to a lesser decrease in affinity, as in the case of derivatives with five atoms in the spacer, 25-27, and in particular for the 1-(2methoxyphenyl)piperazine compound 26. It can therefore be stated that, unlike the buspirone analogues and in agreement with Al-Bermawy,10 for the amido derivatives in this paper, the terminal amide function of longchain piperazines is not important for binding, and its removal yields high-affinity 5-HT1A receptor agents.

N-[2-(4-Phenylpiperazin-1-yl)ethyl]-5-methoxy-1,2,3,4tetrahydronaphthalene-1-carboxamide (22). This compound was prepared in a 73% yield from 4-(2-aminoethyl)-1phenylpiperazine (11) (0.68 g, 3.3 mmol) according to the general procedure: 1H NMR (CDCl3) 1.57-1.87 and 2.28-2.37 (mm, 4H, endo CH2CH2), 2.41-2.58 and 2.65-2.81 [mm, 8H, benzyl CH2, CH2N(CH2)2], 2.98 [br t, 4H, (CH2)2NAr], 3.243.37 (m, 2H, NHCH2), 3.62-3.66 (s + t, 4H, CHCO, CH3), 6.10 (br s, 1H, NH), 6.62-7.32 (mm, 8H, aromatic); GC/MS m/z 394 (M+ + 1, 1), 393 (M+, 5), 188 (13), 175 (100), 132 (27). N-[2-[4-(2-Methoxyphenyl)piperazin-1-yl]ethyl]-5-methoxy-1,2,3,4-tetrahydronaphthalene-1-carboxamide (23). This compound was prepared according to the general procedure (59% yield) by starting from 4-(2-aminoethyl)-1-(2-methoxyphenyl)piperazine (12) (0.75 g, 3.2 mmol): 1H NMR (CDCl3) 1.63-1.89 and 2.29-2.36 (mm, 4H, endo CH2CH2), 2.41-2.58 and 2.73-2.80 [mm, 8H, benzyl CH2, CH2N(CH2)2], 2.86 [br s, 4H, (CH2)2NAr], 3.26-3.32 (m, 2H, NHCH2), 3.65 (br t, 1H, CHCO), 3.73 and 3.83 (2 s, 6H, 2 CH3), 6.09 (br s, 1H, NH), 6.68-7.14 (mm, 7H, aromatic); GC/MS m/z 424 (M+ + 1, 5), 423 (M+, 19), 206 (13), 205 (100), 190 (17). N-[2-[4-(2-Pyridyl)piperazin-1-yl]ethyl]-5-methoxy1,2,3,4-tetrahydronaphthalene-1-carboxamide (24). This compound was synthesized from 4-(2-aminoethyl)-1-(2-pyridyl)piperazine (13) (0.62 g, 3.0 mmol) according to the general procedure (73% yield): 1H NMR (CDCl3) 1.58-1.93 and 2.282.36 (mm, 4H, endo CH2CH2), 2.38-2.82 [mm, 8H, benzyl CH2, CH2N(CH2)2], 3.24-3.44 [mm, 6H, (CH2)2NAr, NHCH2], 3.633.68 (s + t, 4H, CHCO, CH3), 6.04 (br s, 1H, NH), 6.58-7.48 (mm, 6H, aromatic), 8.16-8.18 (m, 1H, aromatic NdCH); GC/ MS m/z 395 (M+ + 1, 9), 394 (M+, 32), 232 (22), 176 (100), 147 (38), 127 (29), 121 (60). N-[3-(4-Phenylpiperazin-1-yl)-n-propyl]-5-methoxy1,2,3,4-tetrahydronaphthalene-1-carboxamide (25). Using the general procedure described above, from 4-(3-aminon-propyl)-1-phenylpiperazine (14) (1.05 g, 4.8 mmol), this compound was obtained in a 68% yield: 1H NMR (CDCl3) 1.63-1.95 and 2.12-2.22 (mm, 6H, endo CH2CH2, CH2CH2CH2), 2.50-2.75 [mm, 8H, benzyl CH2, CH2N(CH2)2], 3.16 [br t, 4H, (CH2)2NAr], 3.22-3.40 (m, 2H, NHCH2), 3.64 (t, 1H, J ) 5.5 Hz, CHCO), 3.68 (s, 3H, CH3), 6.34 (br t, 1H, NH), 6.637.30 (mm, 8H, aromatic); GC/MS m/z 408 (M+ + 1, 10), 407 (M+, 37), 392 (67), 289 (21), 275 (100), 246 (45), 175 (41), 161 (39). N-[3-[4-(2-Methoxyphenyl)piperazin-1-yl]-n-propyl]-5methoxy-1,2,3,4-tetrahydronaphthalene-1-carboxamide (26). This compound was prepared from 4-(3-amino-npropyl)-1-(2-methoxyphenyl)piperazine (15) (0.90 g, 3.6 mmol) according to the general procedure (72% yield): 1H NMR (CDCl3) 1.69-1.96 and 2.13-2.22 (mm, 6H, endo CH2CH2, CH2CH2CH2), 2.45-2.77 [mm, 8H, benzyl CH2, CH2N(CH2)2], 2.96 [br s, 4H, (CH2)2NAr], 3.28-3.35 (m, 2H, NHCH2), 3.65 (t, 1H, J ) 5.4 Hz, CHCO), 3.72 and 3.83 (2 s, 6H, 2 CH3), 6.26 (br t, 1H, NH), 6.66-7.14 (mm, 7H, aromatic); GC/MS m/z 438 (M+ + 1, 15), 437 (M+, 53), 423 (27), 422 (100), 288 (32), 276 (26), 275 (87), 246 (44), 205 (73), 190 (32), 161 (35). N-[3-[4-(2-Pyridyl)piperazin-1-yl]-n-propyl]-5-methoxy1,2,3,4-tetrahydronaphthalene-1-carboxamide (27). This compound was synthesized as above from 4-(3-amino-n-propyl)-1-(2-pyridyl)piperazine (16) (1.06 g, 4.8 mmol) (64% yield): 1H NMR (CDCl3) 1.57-1.94 and 2.15-2.27 (mm, 6H, endo CH2CH2, CH2CH2CH2), 2.30-2.74 [mm, 8H, benzyl CH2, CH2N(CH2)2], 3.21-3.48 [mm, 6H, (CH2)2NAr, NHCH2], 3.573.77 (s + t, 4H, CHCO, CH3), 6.23 (br s, 1H, NH), 6.56-7.48 (mm, 6H, aromatic), 8.14-8.17 (m, 1H, aromatic NdCH); GC/ MS m/z 409 (M+ + 1, 14), 408 (M+, 51), 406 (40), 314 (43), 289 (39), 246 (68), 161 (51), 107 (100). N-Methyl-N-[2-(4-phenylpiperazin-1-yl)ethyl]-5-methoxy-1,2,3,4-tetrahydronaphthalene-1-carboxamide (28). This compound was obtained in a 68% yield according to the general procedure starting from 4-[2-(methylamino)ethyl]-1phenylpiperazine (17) (1.45 g, 6.6 mmol): 1H NMR (DMSOd6)20 1.56-1.91 (mm, 4H, endo CH2CH2), 2.53-2.67 [mm, 8H, benzyl CH2, CH2N(CH2)2], 2.90 and 3.13 (2 s, 3H, NCH3), 3.11 [br t, 4H, (CH2)2NAr], 3.32-3.41 and 3.56-3.69 [2 m, 2H, N(CH3)CH2], 3.74 (s, 3H, OCH3), 4.11 (br s, 1H, CHCO), 6.50-

Experimental Section Chemistry. Column chromatographies were performed with 1:30 ICN silica gel 60A (63-200 µm) as the stationary phase. Melting points were determined in open capillaries on a Gallenkamp electrothermal apparatus. Elemental analyses were performed by the Microanalytical Section of our department on solid samples only; the analytical results (C,H,N) were within (0.4% of the theoretical values. 1H NMR spectra were recorded on a Bruker AM 300 WB instrument. Chemical shifts are reported in parts per million (ppm, δ). Recording of mass spectra was done on a HP 5995C gas chromatograph/mass spectrometer, electron impact 70 eV, equipped with HP59970A workstation; only significant m/z peaks, with their percent relative intensity in parentheses, are herein reported. All compounds had NMR and mass spectra that were fully consistent with their structure. 5-Methoxy-1,2,3,4-tetrahydronaphthalene-1-carboxylic Acid (9). A mixture of 5-methoxy-1-tetralone (8) (12.5 g, 71 mmol), zinc iodide (0.50 g), and trimethylsilyl cyanide (25.0 g, 252 mmol) was stirred for 48 h at room temperature under nitrogen. The reaction mixture was diluted with CHCl3 and washed with an aqueous NaHCO3 saturated solution. The separated organic layer was dried over Na2SO4 and concentrated under reduced pressure to give the crude trimethylsilyl cyanohydrin that was chromatographed (petroleum ether/ethyl acetate, 9:1, as eluent). The trimethylsilyl cyanohydrin of 8 (18.4 g, 66.8 mmol) was heated at 140 °C for 65 h in the presence of tin(II) chloride dihydrate (65.0 g, 288 mmol), glacial acetic acid (60 mL), and concentrated hydrochloric acid (60 mL). The reaction mixture was cooled and diluted with 250 mL of CHCl3; then the layers were separated, and the aqueous layer was back-extracted with ether. The basic aqueous layer was cooled, acidified, and extracted three times with CHCl3. The combined organic layers were dried (Na2SO4) and concentrated in vacuo to give a crude product that was chromatographed (CH2Cl2/MeOH, 19:1, as eluent) to afford pure 9 as a pale yellow solid (6.06 g, 44% yield): mp 105-106 °C (from petroleum ether); 1H NMR (CDCl3) 1.72-2.51 (mm, 4H, endo CH2CH2), 2.53-2.79 (mm, 2H, benzyl CH2), 3.76-3.87 (s + m, 4H, CHCO, CH3), 6.71-7.15 (mm, 3H, aromatic), 10.80 (br s, 1H, OH, D2O exchanged); GC/MS m/z 207 (M+ + 1, 6), 206 (M+, 50), 161 (100), 160 (30), 115 (23), 91 (27). General Procedure for the Preparation of Amides 2230. To a stirred solution of 5-methoxy-1,2,3,4-tetrahydronaphthalene-1-carboxylic acid (9) (0.52 g, 2.5 mmol) and DCC (0.68 g, 3.3 mmol) in CH2Cl2 was added dropwise a solution of the appropriate amine 11-19 (3.0 mmol), in the same solvent. The reaction mixture was stirred overnight at room temperature; then a few milliliters of glacial acetic acid was added to decompose the excess reagent. The insoluble urea was removed by filtration, the filtrate was washed with 2 N NaOH, and the organic layer was separated and dried over Na2SO4. Evaporation of the solvent in vacuo provided the crude amide which was chromatographed (CH2Cl2/MeOH, 19:1, as eluent) to give the expected pure amides 22-30 as almost white to pale yellow semisolids.

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7.22 (mm, 8H, aromatic); GC/MS m/z 408 (M+ + 1, 3), 407 (M+, 13), 188 (31), 175 (100), 132 (21). N-[2-[4-(2-Methoxyphenyl)piperazin-1-yl]ethyl]-N-methyl-5-methoxy-1,2,3,4-tetrahydronaphthalene-1-carboxamide (29). This compound was prepared from 1-(2-methoxyphenyl)-4-[2-(methylamino)ethyl]piperazine (18) (0.72 g, 3.3 mmol) as above (78% yield): 1H NMR (DMSO-d6)20 1.59-1.92 (mm, 4H, endo CH2CH2), 2.52-2.64 [mm, 8H, benzyl CH2, CH2N(CH2)2], 2.90 and 3.14 (2 s, 3H, NCH3), 2.94 [br s, 4H, (CH2)2NAr], 3.34-3.39 and 3.55-3.68 [2 m, 2H, N(CH3)CH2], 3.74 and 3.76 (2 s, 6H, 2 OCH3), 4.11 (br t, 1H, CHCO), 6.517.06 (mm, 7H, aromatic); GC/MS m/z 438 (M+ + 1, 2), 437 (M+, 6), 218 (20), 205 (100), 190 (20). N-Methyl-N-[3-(4-phenylpiperazin-1-yl)-n-propyl]-5methoxy-1,2,3,4-tetrahydronaphthalene-1-carboxamide (30). This compound was prepared according to the general procedure (60% yield) from 4-[3-(methylamino)-npropyl]-1-phenylpiperazine (19) (1.35 g, 5.8 mmol): 1H NMR (DMSO-d6)20 1.57-1.89 (mm, 6H, endo CH2CH2, CH2CH2CH2), 2.27-2.64 [mm, 8H, benzyl CH2, CH2N(CH2)2], 2.87 and 3.12 (2 s, 3H, NCH3), 3.04-3.11 [mm, 4H, (CH2)2NAr], 3.35 and 3.49 [2 br t, 2H, N(CH3)CH2], 3.74 and 3.75 (2 s, 3H, OCH3), 4.11 and 4.18 (2 br t, 1H, CHCO), 6.43-7.21 (mm, 8H, aromatic); GC/MS m/z 422 (M+ + 1, 7), 421 (M+, 25), 419 (30), 406 (47), 303 (29), 289 (100), 260 (73), 258 (27), 175 (38), 161 (61). 4-[N-[(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)methyl]-2-aminoethyl]-1-phenylpiperazine (31). To a stirred suspension of LiAlH4 (0.10 g, 2.6 mmol) in anhydrous THF (20 mL) was added amide 22 (1.02 g, 2.6 mmol), in the same solvent. The reaction mixture was refluxed for 2 h. After cooling, a few drops of water was added, the suspension was filtered, and the filtrate was concentrated under reduced pressure. The residue was diluted with water and extracted twice with CH2Cl2. The separated organic layers were dried over Na2SO4 and concentrated under reduced pressure to give a crude residue which was chromatographed (CH2Cl2/MeOH, 19:1, as eluent). Pure 31 was a pale yellow oil (0.45 g, 46% yield): 1H NMR (CDCl3) 1.74-1.87 (mm, 4H, endo CH2CH2), 2.49-2.75 [mm, 9H, benzyl CH2, CH2N(CH2)2, NH, 1H, D2O exchanged], 2.87 (br t, 2H, NHCH2CH2), 2.93 (d, 2H, J ) 3.4 Hz, CHCH2NH), 3.08-3.10 (mm, 5H, (CH2)2NAr, CHCH2NH), 3.75 (s, 3H, CH3), 6.62-7.31 (mm, 8H, aromatic); GC/MS m/z 380 (M+ + 1, 1), 379 (M+, 3), 261 (22), 247 (21), 218 (60), 176 (37), 175 (100). General Procedure for the Preparation of Amines 3235. The following compounds were prepared and purified according to the method described for compound 3,1 starting from 5-methoxy-1-tetralone (8) and 4-(2-aminoethyl)-1-phenylpiperazine (11), 4-(2-aminoethyl)-1-(2-pyridyl)piperazine (13), 4-(3-amino-n-propyl)-1-phenylpiperazine (14), and 4-(3amino-n-propyl)-1-(2-methoxyphenyl)piperazine (15), respectively. 4-[N-(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-2aminoethyl]-1-phenylpiperazine (32): 1H NMR (CDCl3) 1.68-1.98 (mm, 5H, endo CH2CH2, NH, 1H, D2O exchanged), 2.48-2.88 [mm, 10H, CH2CH2N(CH2)2, benzyl CH2], 3.18 [br t, 4H, (CH2)2NAr], 3.75-3.79 (s + t, 4H, CH3, CHNH), 6.687.29 (mm, 8H, aromatic); GC/MS m/z 366 (M+ + 1, 1), 365 (M+, 3), 176 (56), 175 (78), 162 (20), 161 (100), 132 (37). 4-[N-(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-2aminoethyl]-1-(2-pyridyl)piperazine (33): 1H NMR (CDCl3) 1.68-2.01 (mm, 5H, endo CH2CH2, NH, 1H, D2O exchanged), 2.48-2.88 [mm, 10H, CH2CH2N(CH2)2, benzyl CH2], 3.51 [br t, 4H, (CH2)2NAr], 3.55-3.79 (s + t, 4H, CH3, CHNH), 6.587.48 (mm, 6H, aromatic), 8.16-8.18 (m, 1H, aromatic NdCH); GC/MS m/z 367 (M+ + 1, 2), 366 (M+, 9), 177 (23), 176 (100), 161 (72), 147 (44), 121 (76). 4-[N-(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-3amino-n-propyl]-1-phenylpiperazine (34): 1H NMR (CDCl3) 1.69-1.98 (mm, 7H, endo CH2CH2, CH2CH2CH2, NH, 1H, D2O exchanged), 2.41-2.85 [mm, 10H, NHCH2, CH2N(CH2)2, benzyl CH2], 3.16 [br t, 4H, (CH2)2NAr], 3.70-3.81 (s + t, 4H, CH3, CHNH), 6.66-7.28 (mm, 8H, aromatic); GC/MS m/z 380 (M+ + 1, 1), 379 (M+, 6), 247 (72), 245 (33), 189 (33), 176 (47), 175 (92), 161 (100), 160 (30).

1-(2-Methoxyphenyl)-4-[N-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-3-amino-n-propyl]piperazine (35): 1H NMR (CDCl ) 1.68-1.97 (mm, 7H, endo CH CH , CH CH 3 2 2 2 2 CH2, NH, 1H, D2O exchanged), 2.44-2.84 [mm, 10H, NHCH2, CH2N(CH2)2, benzyl CH2], 3.06 [br s, 4H, (CH2)2NAr], 3.73 (br t, 1H, CHNH), 3.78 and 3.84 (2 s, 6H, 2 CH3), 6.67-7.14 (mm, 7H, aromatic); GC/MS m/z 410 (M+ + 1, 1), 409 (M+, 3), 261 (29), 247 (59), 245 (31), 219 (35), 205 (100), 190 (46), 161 (87). 1-(2-Methoxyphenyl)-4-[2-[N-(5-methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)methylamino]ethyl]piperazine (36). To a solution of 1-(2-methoxyphenyl)-4-[N-(5-methoxy-1,2,3,4tetrahydronaphthalen-1-yl)-2-aminoethyl]piperazine (3) (2.01 g, 5.1 mmol) in 50 mL of CHCl3 was added 50 mL of 2.4% aqueous NaOH. Then methyl chloroformate (0.79 mL, 10.2 mmol) in CHCl3 was added dropwise to the ice-cooled mixture, under vigorous stirring. The cold mixture was stirred for 1 h and then acidified with 6 N HCl and stirred at 25 °C for 0.5 h. The layers were separated, and the aqueous portion was extracted with CHCl3. The organic portions were combined, washed first with aqueous NaHCO3 and then with water, dried over Na2SO4, and concentrated under reduced pressure to yield the oily carbamate derivative. To a stirred suspension of LiAlH4 (0.39 g, 10.3 mmol) in anhydrous THF was added a solution of the carbamate derivative in the same solvent. The mixture was refluxed for 24 h and then cooled, and the excess reagent was decomposed with a few drops of water. The mixture was filtered and the filtrate concentrated under reduced pressure. The residue was diluted with CHCl3 and washed with water. The separated organic layer was dried over Na2SO4 and evaporated in vacuo to afford the Nmethylated derivative 36 (1.76 g, 84% yield): 1H NMR (CDCl3) 1.53-1.62 and 1.93-2.05 (mm, 4H, endo CH2CH2), 2.27 (s, 3H, NCH3), 2.38-2.81 [mm, 10H, NHCH2, CH2N(CH2)2, benzyl CH2], 3.08 [br s, 4H, (CH2)2NAr], 3.79 and 3.90 (m + 2 s, 7H, 2 CH3, CHNH), 6.65-7.35 (mm, 7H, aromatic); GC/MS m/z 410 (M+ + 1, 1), 409 (M+, 4), 205 (31), 204 (25), 161 (100). N-(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)bromoacetamide (20). A cooled solution of 5-methoxy-1,2,3,4tetrahydro-1-naphthalenamine (10) (2.50 g, 14.1 mmol) in CH2Cl2, was stirred vigorously with 2% aqueous NaOH (18.3 mmol) while bromoacetyl chloride (1.59 mL, 18.3 mmol) in CH2Cl2 was added dropwise. The same NaOH solution was then used in drops to maintain pH at 9, and at costant pH the layers were separated. The organic phase was washed with 3 N HCl and water and then dried over Na2SO4 and evaporated under reduced pressure. The crude residue was eluted with CHCl3 to give compound 20 as a white solid (3.23 g, 77% yield): mp 166-167 °C (from CHCl3/n-hexane); 1H NMR (CDCl3) 1.731.93 and 1.95-2.05 (mm, 4H, endo CH2CH2), 2.55-2.75 (m, 2H, benzyl CH2), 3.81 (s, 3H, CH3), 3.88 (s, 2H, CH2Br), 5.085.14 (m, 1H, CHNH), 6.67-7.18 (mm, 4H, aromatic, NH); GC/ MS m/z 299 (M+ + 2, 3), 297 (M+, 3), 176 (14), 160 (100), 159 (26). N-(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-3-chloropropanamide (21). This compound was prepared from compound 10 (5.12 g, 28.9 mmol), 2% aqueous NaOH (37.7 mmol), and 3-chloropropionyl chloride (3.60 mL, 37.7 mmol) as for compound 20. The crude residue was chromatographed (CHCl3/ethyl acetate, 9:1, as eluent) to give compound 21 as a white solid (5.52 g, 71% yield): mp 167-168 °C (from Et2O); 1H NMR (CDCl ) 1.73-2.01 (mm, 4H, endo CH CH ), 2.523 2 2 2.73 (m + t, 4H, benzyl CH2, COCH2), 3.73-3.86 (m + s, 5H, CH3, CH2Cl), 5.12-5.18 (m, 1H, CHNH), 5.95 (br d, 1H, NH), 6.69-7.15 (mm, 3H, aromatic); GC/MS m/z 269 (M+ + 2, 2), 268 (M+ + 1, 1), 267 (M+, 5), 160 (100), 159 (25). N-(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-4-phenylpiperazinoacetamide (37). The derivative 20 (2.03 g, 6.8 mmol) was refluxed overnight with 1-phenylpiperazine (2.21 g, 13.6 mmol) and a slight excess of NaHCO3 in acetonitrile. After cooling, the mixture was concentrated under reduced pressure, and the residue was taken up with water and extracted with CHCl3. The chloroform phase was dried over Na2SO4, the solvent was evaporated, and the crude residue was chromatographed (CH2Cl2/MeOH, 19:1, as eluent) to give 37 as a pale yellow semisolid (2.47 g, 96% yield): 1H NMR (CDCl3) 1.72-1.86 and 1.97-2.04 (mm, 4H, endo CH2-

1-Aryl-4-[(1-tetralinyl)alkyl]piperazines

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CH2), 2.56-2.73 [mm, 6H, benzyl CH2, CH2N(CH2)2], 3.11 [br s, 6H, (CH2)2NAr, CH2N(CH2)2], 3.80 (s, 3H, CH3), 5.15-5.28 (m, 1H, CHNH), 6.70-7.26 (mm, 8H, aromatic), 7.37 (br d, 1H, NH); GC/MS m/z 380 (M+ + 1, 6), 379 (M+, 25), 175 (100), 161 (26), 132 (26). N-(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-4-phenylpiperazinopropanamide (38). This compound was obtained as described for compound 37 (0.92 g, 59% yield) starting from derivative 21 (1.44 g, 3.9 mmol) and 1-phenylpiperazine (1.27 g, 7.8 mmol): 1H NMR (CDCl3) 1.72-1.96 (mm, 4H, endo CH2CH2), 2.42 [t, 2H, J ) 6.0 Hz, CH2N(CH2)2], 2.46-2.60 [mm, 6H, benzyl CH2, CH2N(CH2)2], 2.66 (t, 2H, J ) 5.9, COCH2), 2.80-2.95 [mm, 4H, (CH2)2NAr], 3.69 (s, 3H, CH3), 5.05-5.11 (m, 1H, CHNH), 6.61-7.26 (mm, 8H, aromatic), 8.70 (br d, 1H, NH); GC/MS m/z 394 (M+ + 1, 8), 393 (M+, 29), 378 (60), 275 (24), 161 (100), 160 (27). N-(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-4-(2methoxyphenyl)piperazinopropanamide (39). This compound was prepared according to the method described for compound 38 (1.40 g, 52% yield) starting from 21 (1.67 g, 6.2 mmol) and 1-(2-methoxyphenyl)piperazine (2.38 g, 12.4 mmol): 1H NMR (CDCl3) 1.72-1.94 (mm, 4H, endo CH2CH2), 2.41 [t, 2H, J ) 6.0 Hz, CH2N(CH2)2], 2.47-2.80 [mm, 12H, benzyl CH2, CH2N(CH2)2, (CH2)2NAr, COCH2], 3.74 and 3.81 (2 s, 6H, 2 CH3), 5.05-5.11 (m, 1H, CHNH), 6.65-7.12 (mm, 7H, aromatic), 8.96 (br d, 1H, NH); GC/MS m/z 424 (M+ + 1, 11), 423 (M+, 41), 409 (27), 408 (100), 205 (27), 191 (21), 161 (66), 160 (31). N-(5-Methoxy-1,2,3,4-tetrahydronaphthalen-1-yl)-4-(2pyridyl)piperazinopropanamide (40). Compound 40 was synthesized (1.34 g, 61% yield) starting from 21 (1.50 g, 5.6 mmol) and 1-(2-pyridyl)piperazine (1.83 g, 11.2 mmol): 1H NMR (CDCl3) 1.73-2.01 (mm, 4H, endo CH2CH2), 2.44 [t, 2H, J ) 6.0 Hz, CH2N(CH2)2], 2.48-2.58 [mm, 6H, benzyl CH2, CH2N(CH2)2], 2.66 (t, 2H, J ) 5.8 Hz, COCH2), 3.22-3.32 [mm, 4H, (CH2)2NAr], 3.71 (s, 3H, CH3), 5.07-5.28 (m, 1H, CHNH), 6.53-7.48 (mm, 6H, aromatic), 8.13-8.17 (m, 1H, aromatic NdCH), 8.56 (br s, 1H, NH); GC/MS m/z 395 (M+ + 1, 8), 394 (M+, 31), 392 (22), 300 (61), 275 (55), 176 (29), 161 (97), 160 (87), 127 (46), 121 (31), 119 (22), 107 (100). Hydrochloride Salts: General Procedure. The hydrochloride salts were prepared by adding an HCl ethereal solution to a methanolic solution of amine. Recrystallization solvents, crystallization formulas, and melting points are listed in Table 1. They were obtained as white to sandy yellow crystals or crystalline powders. Pharmacological Methods. All binding studies were performed in rat brain areas. Male Wistar rats, weighing 175-200 g, were killed by decapitation under light anesthesia and the various brain regions dissected out very quickly on an ice-cold plate. Depending on the receptor to be studied, the different areas were used following the methods described in the next paragraphs. D-1 Dopaminergic Binding Assay. The binding assay for D-1 dopaminergic receptors was essentially that described by Billard et al.21 Corpora striata were homogenized in 30 vol (w/v) of ice-cold 50 mM Tris‚HCl buffer (pH 7.7 at 25 °C) using a Polytron PT10 homogenizer (setting 5 for 20 s). Homogenates were centrifuged twice for 10 min at 50000g with resuspension of the pellet in fresh buffer. The final pellet was resuspended in ice-cold Tris‚HCl (50 mM) containing 120 mM NaCl, 5 mM KCl, 2 mM CaCl2, 1 mM MgCl2, 0.1% ascorbic acid, and 10 µM pargyline (pH 7.1 at 37 °C). Each assay tube contained 50 µL of drug solution, 50 µL of [3H]SCH-23390 to achieve a final concentration of 0.4 nM, and 900 µL of resuspended membranes (3 mg of fresh tissue). The tubes were incubated for 15 min at 37 °C, and the incubation was terminated by rapid filtration under vacuum through Whatman GF/B glass fiber filters. The filters were washed three times with 5 mL of ice-cold 50 mM Tris‚HCl buffer (pH 7.7 at 25 °C). The radioactivity bound to the filters was measured by a liquid scintillation counter. Specific [3H]SCH-23390 binding was defined as the difference between binding in the absence or presence of 0.1 µM piflutixol. D-2 Dopaminergic Binding Assay. The procedure used in radioligand binding assay has been published in detail by

Creese et al.22 Corpora striata were homogenized in 30 vol (w/v) of ice-cold 50 mM Tris‚HCl buffer (pH 7.7 at 25 °C) using a Polytron PT10 homogenizer (setting 5 for 20 s). Homogenates were centrifuged twice for 10 min at 50000g with resuspension of the pellet in fresh buffer. The final pellet was resuspended in ice-cold Tris‚HCl (50 mM) containing 120 mM NaCl, 5 mM KCl, 2 mM CaCl2, 1 mM MgCl2, 0.1% ascorbic acid, and 10 µM pargyline (pH 7.1 at 37 °C). Each assay tube contained 50 µL of drug solution, 50 µL of [3H]spiroperidol to achieve a final concentration of 0.4 nM, and 900 µL of resuspended membranes (3 mg of fresh tissue). The tubes were incubated for 15 min at 37 °C, and the incubation was terminated by rapid filtration under vacuum through Whatman GF/B glass fiber filters. The filters were washed three times with 5 mL of ice-cold 50 mM Tris‚HCl buffer (pH 7.7 at 25 °C). The radioactivity bound to the filters was measured by a liquid scintillation counter. Specific [3H]spiroperidol binding was defined as the difference between binding in the absence or presence of 1 µM (+)-butaclamol. 5-HT1A Serotonergic Binding Assay. The procedure used in radioligand binding assay has been published in detail by Hall et al.23 Hippocampus was homogenized in 30 vol (w/v) of ice-cold 50 mM Tris‚HCl buffer (pH 7.2 at 25 °C) using a Polytron PT10 homogenizer (setting 5 for 20 s). Homogenates were centrifuged twice for 10 min at 50000g with resuspension of the pellet in fresh buffer. After the second centrifugation, the pellet was resuspended in homogenization buffer and the suspension incubated 10 min at 37 °C. After it had been centrifuged and washed twice more, the final pellet was resuspended in ice-cold Tris‚HCl (50 mM) containing 4 mM CaCl2, 0.1% ascorbic acid, and 10 µM pargyline (pH 7.4 at 25 °C). Each assay tube contained 50 µL of drug solution, 50 µL of [3H]-8-OH-DPAT to achieve a final concentration of 0.8 nM, and 900 µL of resuspended membranes (10 mg of fresh tissue). The tubes were incubated for 30 min at 25 °C, and the incubation was terminated by rapid filtration under vacuum through Whatman GF/B glass fiber filters. The filters were washed three times with 5 mL of ice-cold 50 mM Tris‚HCl buffer (pH 7.2 at 25 °C). The radioactivity bound to the filters was measured by a liquid scintillation counter. Specific [3H]8-OH-DPAT binding was defined as the difference between binding in the absence or presence of 10 µM 5-HT. 5-HT2 Serotonergic Binding Assay. The procedure used in radioligand binding assay has been published in detail by Leysen et al.24 Prefrontal cortex was homogenized in 30 vol (w/v) of ice-cold 50 mM Tris‚HCl buffer (pH 7.2 at 25 °C) using a Polytron PT10 homogenizer (setting 5 for 20 s). Homogenates were centrifuged three times for 10 min at 50000g with resuspension of the pellet in fresh buffer. The final pellet was resuspended in ice-cold 50 mM Tris‚HCl (pH 7.4 at 37 °C). Each assay tube contained 50 µL of drug solution, 50 µL of [3H]ketanserin to achieve a final concentration of 0.8 nM, and 900 µL of resuspended membranes (5 mg of fresh tissue). The tubes were incubated for 15 min at 37 °C, and the incubation was terminated by rapid filtration under vacuum through Whatman GF/B glass fiber filters. The filters were washed three times with 5 mL of ice-cold 50 mM Tris‚HCl buffer (pH 7.2 at 25 °C). The radioactivity bound to the filters was measured by a liquid scintillation counter. Specific [3H]ketanserin binding was defined as the difference between binding in the absence or presence of 1 µM methysergide. r1-Adrenergic Binding Assay. The procedure used in radioligand binding assay has been published in detail by Greengrass and Bremner.25 Brain cortex was homogenized in 30 vol (w/v) of ice-cold 50 mM Tris‚HCl buffer (pH 7.2 at 25 °C) using a Polytron PT10 homogenizer (setting 5 for 20 s). Homogenates were centrifuged twice for 10 min at 50000g with resuspension of the pellet in fresh buffer. The final pellet was resuspended in ice-cold 50 mM Tris‚HCl (pH 7.4 at 25 C°). Each assay tube contained 50 µL of drug solution, 50 µL of [3H]prazosin to achieve a final concentration of 0.4 nM, and 900 µL of resuspended membranes (10 mg of fresh tissue). The tubes were incubated for 30 min at 25 °C, and the incubation was terminated by rapid filtration under vacuum through Whatman GF/B glass fiber filters. The filters were washed

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three times with 5 mL of ice-cold 50 mM Tris‚HCl buffer (pH 7.2 at 25 °C). The radioactivity bound to the filters was measured by a liquid scintillation counter. Specific [3H]prazosin binding was defined as the difference between binding in the absence or presence of 1 µM phentolamine. r2-Adrenergic Binding Assay. The procedure used in radioligand binding assay has been published in detail by Perry and U’Prichard.26 Brain cortex was homogenized in 30 vol (w/v) of ice-cold 5 mM Tris‚HCl, 5 mM EDTA buffer (pH 7.3 at 25 °C) using a Polytron PT10 homogenizer (setting 5 for 20 s). Homogenates were centrifuged three times for 10 min at 50000g with resuspension of the pellet in fresh buffer. The final pellet was resuspended in ice-cold 50 mM Tris‚HCl, 0.5 mM EDTA (pH 7.5 at 25 °C). Each assay tube contained 50 µL of drug solution, 50 µL of [3H]yohimbine to achieve a final concentration of 1 nM, and 900 µL of resuspended membranes (10 mg of fresh tissue). The tubes were incubated for 30 min at 25 °C, and the incubation was terminated by rapid filtration under vacuum through Whatman GF/B glass fiber filters. The filters were washed three times with 5 mL of ice-cold 50 mM Tris‚HCl, 0.5 mM EDTA buffer (pH 7.5 at 25 °C). The radioactivity bound to the filters was measured by a liquid scintillation counter. Specific [3H]yohimbine binding was defined as the difference between binding in the absence or presence of 10 µM phentolamine.

Acknowledgment. The financial support from CNR is gratefully acknowledged. References (1) For part 2, see: Perrone, R.; Berardi, F.; Colabufo, N. A.; Leopoldo, M.; Tortorella, V.; Fiorentini, F.; Olgiati, V.; Ghiglieri, A.; Govoni, S. High affinity and selectivity on 5-HT1A receptor of 1-aryl-4-[(1-tetralin)alkyl]piperazines. 2. J. Med. Chem. 1995, 38, 942-949. (2) Peroutka, S. J. The molecular pharmacology of 5-hydroxytryptamine receptor subtypes. In Serotonin receptor subtypes: basic and clinical aspect; Peroutka, S. J., Ed.; John Wiley & Sons Ltd.: New York, 1991; pp 65-80. (3) Audia, J. E.; Cohen, M. L. Serotonin modulators and cardiovascular/gastrointestinal diseases. Annu. Rep. Med. Chem. 1991, 26, 103-112. (4) Frazer, A.; Maayani, S.; Wolfe, B. B. Subtypes of receptors for serotonin. Annu. Rev. Pharmacol. Toxicol. 1990, 30, 308-348. (5) Zifa, A.; Fillion, G. 5-Hydroxytryptamine receptors. Pharmacol. Rev. 1992, 44, 401-458. (6) Romero, A. G.; McCall, R. B. Advances in central serotoninergics. Annu. Rep. Med. Chem. 1992, 27, 21-30. (7) Robertson, D. W.; Fuller, R. W. Progress in antidepressant drugs. Annu. Rep. Med. Chem. 1991, 26, 23-32. (8) Glennon, R. A. Concepts for design of 5-HT1A serotonin agonists and antagonists. Drug Dev. Res. 1992, 26, 251-274. (9) Raghupathi, R.; Rydelek-Fitzgerald, L.; Teitler, M.; Glennon, R. A. Analogues of the 5-HT1A serotonin antagonist 1-(2-methoxyphenyl)-4-[4-(2-phthalimido)butyl]piperazine with reduced R1adrenergic affinity. J. Med. Chem. 1991, 34, 2633-2638. (10) El-Bermawy, M.; Raghupathi, R.; Ingher, S. P.; Teitler, M.; Maayani, S.; Glennon, R. A. 4-[4-(1-Noradamantanecarboxamido)butyl]-1-(2-methoxyphenyl)piperazine: a high-affinity 5-HT1A-selective agent. Med. Chem. Res. 1992, 2, 88-95. (11) Cliffe, I. A.; Fletcher, A. Advances in 5-HT1A antagonist research. Drugs Future 1993, 18, 631-642. (12) Orjales, A.; Alonso-Cires, L.; Labeaga, L.; Corco´stegui, R. New (2-methoxyphenyl)piperazine derivatives as 5-HT1A receptor ligands with reduced R1-adrenergic activity. Synthesis and structure-affinity relationships. J. Med. Chem. 1995, 38, 12731277.

Perrone et al. (13) Perrone, R.; Berardi, F.; Colabufo, N. A.; Tortorella, V.; Fiorentini, F.; Olgiati, V.; Vanotti, E.; Govoni, S. Mixed 5-HT1A/D-2 activity of a new model of arylpiperazine: 1-aryl-4-[3-(1,2dihydronaphthalen-4-yl)-n-propyl]piperazines. 1. Synthesis and structure-activity relationships. J. Med. Chem. 1994, 37, 99104. (14) Misztal, S.; Bojarski, A.; Mackowiak, M.; Boksa, J.; Bielecka, Z.; Mokrosz, J. L. Structure-activity relationship studies of CNS agents. 6. Effect of terminal amide fragment on 5-HT1A and 5-HT2 receptor affinity for N-[3-(4-aryl-1-piperazinyl)propyl] derivatives of 3,4-dihydroquinolin-2-(1H)-one and its isomeric isoquinolinones. Med. Chem. Res. 1992, 2, 82-87. (15) Belletire, J. L.; Howard, H.; Donahue, K. A facile synthesis of phenylacetic acids from aryl ketones. Synth. Commun. 1982, 12, 763-770. (16) Perrone, R.; Berardi, F.; Leopoldo, M.; Tortorella, V.; Lograno, M. D.; Daniele, E.; Govoni, S. 5-HT and DA receptor affinity of arylpiperazine derivatives with terminal benzamide fragment. Farmaco 1994, 49, 567-572. (17) Perrone, R.; Berardi, F.; Leopoldo, M.; Tortorella, V.; Lograno, M. D.; Daniele, E.; Govoni, S. 5-HT1A and D-2 receptor affinity of o-methoxyphenylpiperazine derivatives with terminal benzamide fragment on N-4 alkyl chain. 2. Farmaco 1995, 50, 505510. (18) Horner, J. K.; Skinner, W. A. A general method for selective N-methylation of substituted tryptamines. Can. J. Chem. 1966, 44, 315-319. (19) Sarges, R.; Tretter, J. R.; Tenen, S. S.; Weissman, A. 5,8Disubstituted 1-aminotetralins. A class of compounds with a novel profile of central nervous system activity. J. Med. Chem. 1973, 16, 1003-1011. (20) The reported NMR data were obtained at 20 °C. The appearance of spectra recorded at higher temperatures changed as detailed below. Compound 28: The two sharp peaks observed at δ ) 2.90 and 3.13 begin to broaden on raising the temperature; the two peaks merged at 80 °C; the multiplet at δ ) 3.32-3.41 became a broad peak at 70 °C that merged with signals at δ ) 3.563.69 at 80 °C. Compound 29: The two sharp peaks observed at δ ) 2.90 and 3.14 begin to broaden on raising the temperature; the two peaks merged at 80 °C; the multiplet at δ ) 3.34-3.39 became a broad singlet at 70 °C that merged with signals at δ ) 3.55-3.68 at 80 °C. Compound 30: The two sharp peaks observed at δ ) 2.87 and 3.12 begin to broaden on raising the temperature; the two peaks merged at 80 °C; the two broad triplets at δ ) 3.35 and 3.49 merged at 60 °C and coalesced at 80 °C; the two singlets at δ ) 3.74 and 3.75 coalesced at 50 °C; the two broad triplets at δ ) 4.11 and 4.18 merged at 40 °C and coalesced in a broad singlet at 60 °C. Therefore there is evidence that the compounds 28-30 present two stable conformational isomers at room temperature. (21) Billard, W.; Ruperto, V.; Grosby, G.; Iorio, L. C.; Barnett, A. Characterization of the binding of [3H]SCH-23390, a selective D-1 receptor antagonist ligand in rat striatum. Life Sci. 1985, 35, 1885-1893. (22) Creese, I.; Schneider, R.; Snyder, S. H. [3H]Spiroperidol labels dopamine receptors in pituitary and brain. Eur. J. Pharmacol. 1977, 46, 377-381. (23) Hall, M. D.; El Mestikawy, S.; Emerit, M.; Pichat, L.; Hamon, M.; Gozlan, H. [3H]-8-hydroxy-2-(di-n-propylamino)-tetralin binding to pre- and postsynaptic 5-hydroxytryptamine sites in various region of the rat brain. J. Neurochem. 1985, 44, 16851695. (24) Leysen, J. E.; Niemegeers, C. J. E.; van Nueten, J. M.; Laduron, P. M. [3H]-Ketanserin (R 41468) a selective [3H]ligand for serotonin 2 receptor binding sites. Mol. Pharmacol. 1981, 21, 301-314. (25) Greengrass, P.; Bremner, R. Binding characteristics of [3H]prazosin to rat brain R-adrenergic receptors. Eur. J. Pharmacol. 1979, 55, 323-326. (26) Perry, B. D.; U’Prichard, D. C. [3H]Rauwolscine (R-yohimbine): a specific antagonist radioligand for brain R-2-adrenergic receptors. Eur. J. Pharmacol. 1981, 76, 461-464.

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